We found mostly frozen surfaces today, but the sunniest aspects thawed to the silky soft shallow melt freeze commonly known as corn snow in the afternoon. While frozen, the crust is some 25 cm thick and very strong, though the hard, slippery surface conditions are not appealing for most travelers.

Our shear tests showed that the crust, once broken, is not well supported by the thawed and wet melt freeze snow beneath it. Both our AK Block and Rutschblock sheared cleanly 25 cm down, right under the crust, on the first gentle jump (RB4, AK4 Q2) on a 40° SW aspect test slope. Slab test results were #3, taking more than half of the undermined area but breaking somewhat irregularly and without much stored elastic energy.

There were no other signs of slab instability, but the test results indicate that slopes where the slab is softening just enough to give way while retaining enough strength to propagate fracture could still be a problem. In most areas, the slab is staying frozen enough to be relatively strong and not reactive.

Avalanche activity this last week has been mostly glide crack releases. Several were noted, though none were very fresh. Glide activity usually increases with thaw and rain, but can occur at any time. Steer clear of the glide plates and their runouts.

Travelers will find the best snow this week on the groomed runs at Eaglecrest, which have been tilled to provide a soft, loose surface, and on the few slopes angled just right to catch the afternoon sun. They softened enough today for good skiing, but not enough to edge a snowmachine effectively. Cooler temperatures forecast for the weekend may prevent those slopes from thawing though and they are rough and icy when frozen, so take care if you go seeking to harvest the spring corn.

This is a good example of a snowpack that tests weak but snows no signs of instability in observations or slope tests. Remember that stability evaluation has 3 equal components: observations, traveling tests including slope tests, and snowpits. Reliance on pits alone is likely to lead you astray a fair amount of the time.

Today it would lead you to think the snowpack is weaker than it is, but remember that test block evaluation in the Rogers Pass area has shown about a 10% chance of human triggered avalanches with very strong Rutschblock scores of 6 or 7. That means that if you relied only on that one test for your decisionmaking, you would be likely to trigger a slide once every ten outings, far more often than most of us prefer!